


When Sirens Call

by thedoctormollywinchester



Category: Supernatural
Genre: Alpha Castiel, Alpha Castiel/Omega Dean Winchester, Bottom Dean, Human Sacrifice, I will upload tags and archive ratings and warnings as I go, M/M, Mer!fic, Merman Castiel, Merman Dean Winchester, Omega Dean, Omega Dean Winchester, Sacrifice Dean Winchester, Top Castiel, but not gory, so here you go, the fandom needs more merman fics
Language: English
Status: In-Progress
Published: 2017-09-18
Updated: 2017-10-07
Packaged: 2018-12-31 09:26:37
Rating: Not Rated
Warnings: No Archive Warnings Apply
Chapters: 2
Words: 2,643
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/12129465
Author URL: https://archiveofourown.org/users/thedoctormollywinchester/pseuds/thedoctormollywinchester
Summary: This was it. This was the end. After all he had done in his short life, it was all for naught. He was going to die. Die in a watery grave where his father would never know what had happened to him. Die in this oceanic graveyard where he would sink to the rocky bottom and have his bones picked clean by the fish and whatever hellish creatures surely lived there. And oh God, Sammy. His beloved baby brother, who looked up to his older brother no matter what his presentation had been. Who had stared at Dean after his first heat and pronounced with all the force a young boy could muster that he would never let anyone hurt his brother and that he would take care of him as long as he could. Yes, Sammy had all the markings of a proper Alpha. Dean could only hope that Sammy wouldn’t forget him. There wouldn’t even be a body for his family to mourn over. He sobbed as he slowly sunk under the waves, fingertips disappearing from the air.





	1. Chapter 1

“Please don’t!”

“Sorry Omega. A price has to be paid and you’re what the sea wants.”

Captain Metatron Armstrong pushed his graying hair out of his face, staring out at the darkening horizon. He turned back to face the trembling Omega in front of him, steeling his eyes and scowling.

“I told your good-for-nothing father that a ship was no place for an Omega. Bad luck all around but on the sea? Nothing but a curse to itself and the whole damn crew. Your father may be wealthy but he’s just a Beta. Has no real clue about Omegas, not like an Alpha does.”

Dean shivered. It was freezing outside, the wind whipping up the waves and spraying salt water across the worn wooden deck. He’d been stripped of his warm woolen coat and left in nothing but his thin cotton nightshirt. Everything had gone so terribly wrong so very fast. He was just on his way to visit his cousin Benny before the man’s marriage to his beloved Andrea. He knew Captain Armstrong wasn’t thrilled about having an Omega on board but when his father flashed his gold, the haggard seaman had agreed to have Dean on the ship. As the days went by he noticed more and more whispering and hard stares from the different crew members. Heard flashes here and there of, “—what was the captain thinking—“, “—an OMEGA of all things—“, “—the sea is a harsh mistress, she’ll want what is hers—“. He tried to keep out of people’s way as best as he could, fear creeping into his veins at every whisper but trying to believe that the captain would keep him safe. But early this morning he had been torn from his bunk, stripped of his outerwear and shoved upstairs to the upper deck where the rest of the crew was waiting

“Storm’s brewing boy. And it’s a bad ‘un. I’ve seen this before and barely got out alive myself. But –“, he paused, leering at the terror on Dean’s face. “There is a way to stop the storm from killing us all. And that’s to give the sea a sacrifice.”

_No. Oh dear God no._

 “Take him men!” Dean thrashed against the crew to no avail, arms swarming over his body, tying his limbs together with strong hard tugs that threatened to cut off his circulation entirely. He panicked, screaming out in pain as the coarse rope dug into his skin and in growing anger and terror as he was hoisted onto a rough wooden plank that overlooked the churning deep waters.

“Let me go! Please, I’ll do anything!”

“Anything?”, leered the captain’s second mate Alistair Heyerdahl, his pale eyes raking over the trembling figure in front of him.

“Alistair what do you think you’re doing?” Captain Metatron demanded.

“Think about it Captain. The sea may calm down on her own. And then? Just imagine, a warm body to keep you and the crew pleasured at night. Not having to wait until port for some sweet Omega pussy. I dare say he’d make a fine ‘evening companion’.”

Dean spat in his face. “I’d rather die you piece of shit.” Alistair’s sleazy gaze turned venomous as he viciously swiped at his face with his dirty arm.

“Why you little--!”

“Enough Alistair! As fine an piece of Omega ass he is, it’s not worth losing the ship over is it? So shut your trap.” Armstrong turned back to face Dean, his glare as hard as granite. “You won’t go calmly Omega? Can’t even sacrifice yourself with dignity. That’s enough of that sniveling!” He reached down to pick up a rough wooden oar and shoved it at Dean. Dean leaned back as far as he could, trying to escape being shoved overboard but lost his footing. Just a rough scrape of gnarled oak under his foot and his heart lurched in his chest as he stumbled back and fell off of the plank. His instincts tried to kick in, telling him to reach and grasp for the railing but with his arms being tied there was nothing to be done. The faces of the jeering crew was the last thing he saw as he fell down, down into the icy blue depths.

_Splash_

Dean’s body hit the hard water, instantly convulsing in reaction to the freezing water and in trying to save himself. He managed to get a hand free and tried to push himself up but to no avail.

This was it. This was the end. After all he had done in his short life, it was all for naught. He was going to die. Die in a watery grave where his father would never know what had happened to him. Die in this oceanic graveyard where he would sink to the rocky bottom and have his bones picked clean by the fish and whatever hellish creatures surely lived there. And oh God, Sammy. His beloved baby brother, who looked up to his older brother no matter what his presentation had been. Who had stared at Dean after his first heat and pronounced with all the force a young boy could muster that he would never let anyone hurt his brother and that he would take care of him as long as he could. Yes, Sammy had all the markings of a proper Alpha. Dean could only hope that Sammy wouldn’t forget him. There wouldn’t even be a body for his family to mourn over. He sobbed as he slowly sunk under the waves, fingertips disappearing from the air.

Down, down, down he drifts, lungs running out of air, the pressure getting harder. But then, a noise. He opens his eyes, salt water stinging them fiercely and spies a dark figure swimming towards him.

  _Just great. He wouldn’t even drown all the way before some sea monster decided to turn him into human kelp._

As the figure gets closer Dean is sure he is hallucinating now. It swims faster as it notices he’s almost gone. And wait. Are those _fingers_ wrapping around him? They are and they wrap around his upper left arm and with his last precious seconds of consciousness he stares into eyes bluer than the swirling water around him. A rough voice envelopes his dying mind.

_"Omega, I have you. You are safe. Rest my beloved.”_

And with that, Dean finally succumbed, his last thoughts of a velvety gravel voice covering his being with warmth.

               


	2. Chapter 2

Another day gone by. Castiel swam out through the long seaweed strands near the entrance of his den, his mind distracted. Day in and out. Same old, same old. He sighed tiredly. It wasn’t that he was completely alone, on the contrary some days it felt like he had no peace. He had his friends, chiefly Meg, a raven haired sassy Beta mermaid with deep purple scales on her tail and his closest brother Gabriel, a golden tailed Omega merman with an attitude that far outspanned his physical size. But it seemed like there was no change.

Wake up. Leave the den. Go hunting for the day’s food. Meet up with Meg or Gabriel or both sometime during the day and endure their “loving” teasing. The two of them would simply not stop going on and on after him about getting a mate. There had been a time when Castiel was worried that Meg had wanted him as her mate but thankfully that had not been the case. He loved Meg, truly he did, but as a close friend and after a long discussion he had found out that she felt the same way. But now, she and Gabriel took every opportunity to convince him to take a mate. Sure there were mermaids and mermen a plenty but none of them were _right_. None of them had the right smell or the right mannerisms. He wasn’t sure what he was waiting for but he knew he hadn’t met the right one yet. When he found the omega for himself he would know.

All of a sudden, the water darkened around him. He twisted around quickly and then looked up. He was underneath the shadow of a large wooden ship. Swiftly, he found a large rock to hide behind. This was man for sure. Sometimes the large ships passed overhead without bothering anyone but you never knew for sure. Not much was known about them expect for what had been passed along through gossip.

The ship passed along and the water lightened to its original pure blue. Castiel let out a breath he hadn’t known he was holding and swam out from behind his boulder. All of a sudden _SPLASH_. Something dark and wriggling fell from somewhere on top of the ship and plunged into the depths. Castiel’s eyes widened. He had never seen anything be thrown overboard from one of the human’s vessels before. Out of pure curiosity he slowly swam towards whatever it was, still on his guard.

_WARMTH. HOME. SAFE. SWEET. OMEGA._

Castiel reeled back for a second as the most mouthwatering scent he had ever smelled filled his nose and the whole area around him.

_MATE._

Castiel raced towards the figure as fast as his fins could take him. As he drew closer he was overcome with numerous emotions. The first was awe; his mate – _yes that was his mate_ – was stunning. It was a male, the spicy musk in his scent made it obvious. But then – his mate thrashed around and Castiel was aghast. His mate was a human for one thing but his legs were bound with thick rope and though one of his arms was free, the other was trapped against his chest in a harsh attempt at keeping him in place. Rage filled Castiel’s whole being, his mate was here finally and true he was human but it was obvious that someone had been trying to murder his beloved. Suddenly his mate’s eyes opened and Castiel almost couldn’t breathe. His mate had eyes that could have rivaled the greenest gem in all the seven seas. Unfortunately those eyes were filled with pain. With suffering and terror. Just then Castiel reached him and grabbed his mate’s upper left arm.

“Omega, I have you. You are safe. Rest my beloved.” His mate stared blankly and then closed his eyes, a few last small air bubbles escaping from behind his lips.

“No!” Castiel cried, clutching his mate to his body. His mind frantically running, trying to find a way to save the man. All of a sudden, he remembered a story from his youth about the Sea Goddess Amara, who was rumored to have a great righteous anger, but also granted gifts to those truly in need. There were even stories _*oh please let them be more than stories*_  of the goddess granting merhood status to worthy humans. “Oh Goddess,” he prayed, his lips trembling. “Please, please give me the power to save my mate. Give me the chance to show him love and the care that he deserves. Do not let him die, I have only just found him and yet my heart already is his.”  

_“Castiel”_

The merman in question gasped as the form of the Sea Goddess herself appeared before him, her long brown hair flowing about her bare shoulders and a knowing smile upon her ageless face.

_“I have heard your prayer. This is the man you speak of?”_

“Yes Goddess! I – I know that he is human but he smells like home and he is so beautiful and I want, no, I NEED to save him. I’ve been waiting for so long and I want to have a chance to know him, to provide for him and find out what atrocity has occurred to him. Look! He’s bound and he was thrown overboard a ship that just passed above.”

The goddess glanced over the limp body with a soft look in her eyes. _“I will save your mate Castiel. I warn you that the journey for the both of you will not be easy. This man is human and to save him, I must turn him into a merman so that he can survive. He will need your guidance, love and patience as he adjusts to his new life. But I do have confidence that with time and care, the two of you will overcome all obstacles. He may be human but I can see into his essence and I can perceive that he is a good man, full of light and worthy for someone so devoted as yourself. Now, place your hand on his shoulder.”_ Castiel did as she asked and gasped as her felt the power of the Sea Goddess flow through his body. A golden stream of light poured out of his chest, twining itself around his arm, until it reached his mate. The stream whirled all about the human, bathing his and Castiel’s body in pure, iridescent light. Castiel watched in awe as the light wrapped around his beloved’s waist and before his very eyes, the long shapely, if a bit bowlegged, human legs transforming into a strong merman’s tail completely covered with shimmering scales of every shade of green. The last bit of the glow ended with Castiel’s hand on Dean’s shoulder and when he pulled away, his handprint was left imprinted on the Omega’s skin. The former human’s chest started to rise and fall as normal, though his eyes were still shut.

 _“He will be alright now Castiel. But you must take him back to your den and let him rest. He will be weak for a while yet, both with the harrowing experience he had and the strain of the transformation. He may be afraid when he wakes up so stay with him.”_ The goddess’s face lightly beamed as she took in the sight before her; Castiel clutching his mate tightly in his arms with an awestruck gaze going between her and his mate. _“This omega is strong in spirit and soul. A fighter in all the best ways. Cherish him Castiel.”_ And then with outstretched arms, she faded from existence until all that was left was Castiel and the now merman lying in his arms.

Castiel strengthened his grip. “Let’s go home dear one.” And with that he swam as fast as he could without jostling the man in his arms. Castiel’s heart broke as his mate let out occasional little whispers of pain and fear, once uttering aloud, “Please no. No don’t kill me! Alistair no!” Surely this Alistair had been involved in the potential destruction of his mate. Well, there would be plenty of time to deal with _him_ later. Now his mate needed rest and a healthy adjustment to his new life. Finally, Castiel reached his den swimming through the curtain of seaweed fronds that acted as the entrance covering to his home. He reached the living part of his den and laid the omega on his nest of soft seaweed and sweet smelling sea grass that he had woven together, all the while dreaming of the day that he would no longer have to use it alone. Castiel smiled down lovingly at the scene, the new merman curled up on the nest, and then covered him with a blanket of the same soft material. Leaning down he kissed his new mate on the forehead, breathing in the sweet but spicy musk scent.

“And now my cherished one, I will let you rest. But don’t fear, I’m watching over you and will let no harm come to you. Heal up and when you wake I will do everything in my power to help you in any way that I can.” And on that note, Castiel arranged himself nearby on a smaller version of his nest and watched the rise and fall of his mate’s chest waiting for the omega to awake.

 

 

**Author's Note:**

> First Destiel fanfic! Can't believe it's taken so long but here we have it. I will try to upload without huge gaps of time but I'm in college and have a very busy schedule. Hope you all enjoy!


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